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divided by the expected nuclear overlap function TAB b is shown as a function of the number of participant nucleons (Npart). This is compared to curves from Paukkunen and Salgado, where the unmodified CT10 and modified nuclear EPS09 9 parton densities are utilized. It is also compared to curves from Neufeld and Vitev 10 , 11 using the MSTW08 PDF set and modeling energy loss, and to POWHEG 12 interfaced with the PYTHIA parton-shower generator. In figure (b) and (c), the yields dN/dy and d 2 N/dydpT are represented, respectively, as functions of pT and rapidity and are compared to the same predictions as figure (a) when available. In all cases, the PbPb data agrees within uncertainties with a pp POWHEG simulation scaled by the nuclear geometry – none of the subtler initial state effects can be discerned. There is apparently no significant centrality dependence of the Z boson yield. These data confirm that Z boson production is unmodified by the presence of the dense QGP produced in central collisions. The nuclear modification factor (RAA = dN/TAB × dσpp, where dσpp is given by POWHEG) is also computed and found to be consistent with 1 within statistical and systematic uncertainties 13 . Figure 2: The yields of Z → µ + µ − per event: (a) dN/dy divided by the expected nuclear overlap function TAB and as a function of event centrality parametrized as the number of participating nucleons Npart (b) dN/dy versus the Z boson y (c) d 2 N/dydpT versus the Z boson pT . Data points are located horizontally at average values measured within a given bin. Vertical lines (bands) correspond to statistical (systematic) uncertainties. Theoretical predictions are computed within the same bins as the data, and are described in the text. 6 Conclusion The Z boson yield has been measured for the first time in the dimuon channel in heavy-ion collisions. Within uncertainties, (19% in the integrated case, summing the systematic and statistical uncertainties quadratically) no modification was observed with respect to theoretical NLO pQCD proton-proton cross sections scaled by elementary nucleon-nucleon collisions. This measurement establishes the feasibility of carrying out detailed Z-physics studies in heavy-ion collisions with the CMS detector. With upcoming PbPb collisions at higher luminosity and energy, the Z boson promises to be a powerful reference tool for initial state (nuclear PDFs) and final state (Z+jet) processes in nucleus-nucleus collisions at the LHC. References 1. P. Bagnaia et al. [UA2 Collaboration], “Evidence for Z 0 → e + e − at the CERN ¯pp Collider,” Phys. Lett. B 129, 130 (1983). b The nuclear overlap function is equal to the number of elementary nucleon-nucleon binary collisions divided by the elementary NN cross section and can be interpreted as NN equivalent integrated luminosity per AA collision at a given centrality.
2. V. Kartvelishvili, R. Kvatadze and R. Shanidze, “On Z and Z+jet production in heavy ion collisions,” Phys. Lett. B 356, 589 (1995) [arXiv:hep-ph/9505418]. 3. H. Paukkunen and C. A. Salgado, “Constraints for the nuclear parton distributions from Z and W production at the LHC,” JHEP 1103, 071 (2011) arXiv:1010.5392 [hep-ph]. 4. R. B. Neufeld, I. Vitev and B. W. Zhang, “Toward a determination of the shortest radiation length in nature,” arXiv:1010.3708 [hep-ph]. 5. R. Adolphi et al. [CMS Collaboration], “The CMS experiment at the CERN LHC,” JINST 3, S08004 (2008). 6. M. Mulders et al., “Performance of CMS muon measurements in pp collisions at √ s = 7 TeV,” CMS Analysis Note 2010/211 (2010). 7. T. Sjostrand, S. Mrenna, and P. Skands, ”PYTHIA 6.4 physics and manual”, JHEP 05 (2006) 026, arXiv:hep-ph/0603175. 8. V. Khachatryan et al. [CMS Collaboration], “Measurements of Inclusive W and Z Cross Sections in pp Collisions at √ s = 7 TeV,” JHEP 1101, 080 (2011) arXiv:1012.2466 [hepex]. 9. K. J. Eskola, H. Paukkunen, and C. A. Salgado, EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions, JHEP 04 (2009) 065, arXiv:0902.4154. 10. R. B. Neufeld, I. Vitev, and B. W. Zhang, Toward a determination of the shortest radiation length in nature, arXiv:1010.3708. 11. R. B. Neufeld, I. Vitev, and B. W. Zhang, The physics of Z 0 /*γ-tagged jets at the LHC, arXiv:1006.2389. 12. S. Alioli, P. Nason, C. Oleari et al., NLO vector-boson production matched with shower in POWHEG, JHEP 07 (2008) 060, arXiv:0805.4802. 13. S. Chatrchyan et al. [CMS Collaboration], “Study of Z Boson Production in PbPb Collisions at √ sNN = 2.76 TeV” Phys. Rev. Lett. 106, 212301 (2011) arXiv:1102.5435 [nucl-ex].
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2011 QCD and High Energy Interactio
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Proceedings of the XLVIth RENCONTRE
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2011 RENCONTRES DE MORIOND The XLVI
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Foreword Contents 1. Higgs Searches
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1. Higgs
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95% CL Limit/SM 10 1 Tevatron Run I
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Events/5 GeV 6 10 5 10 4 10 3 10 2
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Events / 0.5 CDF Run II Preliminary
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For the most sensitive sub-channel
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Table 1: Table listing the various
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various SM Higgs mass hypotheses. T
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constraints on parameters are given
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Figure 2: Invariant mass of the ele
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Figure 4: CDF Exclusion limits for
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Table 1: Main phases of 2010 commis
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Table 4: Parameter list for early (
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luminosity of 1.2×10 33 cm −2 s
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2 QCD Analysis settings HERA PDFs a
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min 2 - 2 20 15 10 5 0 H1 and ZEUS
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SM σ / σ 95% CL Limit on 3 10 2 1
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NNLO σ/ σSM 95% CL Upper Bound on
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the report of this working group. I
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2.3 The impact of different PDF par
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SUSY Searches at the Tevatron Ph. G
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on the quality (loose or tight) and
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SUSY searches at ATLAS N. Barlow, o
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channel. These results are combined
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Figure 2: The top left plot shows t
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2010 data. Analysis techniques for
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as main discriminator between event
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sign leptons is particularly intere
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N of events 5 10 DATA 10 4 3 10 10
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) [pb] ν e → B(W’ × σ 10 1 -
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2 Searches in the dijet final state
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ing that the neutrinos were the onl
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The Quasi-Classical Model in SU(N)
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g (γ µ kµ) γ µ Aa µ g (pk)
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3. Top
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of their vertex with respect to the
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of about 9%. 3.1 Differential Cross
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Figure 5: Summary of most recent CD
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the minimum number of jets identifi
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where f’s are probability functio
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hood technique, with a simultaneous
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momentum direction of the b quark f
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Events 200 150 100 50 -1 DØ L=5.4
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after all corrections in the M t¯t
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for prompt J/ψ under the fully tra
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2 Events / 20 MeV/c 50 40 30 20 10
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ATLAS - consists of four parts (mon
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5 D mesons High cross-sections of D
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μ +X') [nb/GeV] → b+X → (pp T
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GeV) μ |
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HEAVY FLAVOUR IN A NUTSHELL Robert
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Figure 1: Overlapping constraints o
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Figure 3: Constraints on new physic
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RECENT B PHYSICS RESULTS FROM THE T
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(IP) distributions are fitted separ
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decays CDF extracts Using a 5.94 fb
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Search for B 0 s → µ+ µ − and
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Ref. 10,11 . The expected GL distri
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IN PURSUIT OF NEW PHYSICS WITH B DE
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τK + K −/τBs 1.01 1.00 0.99 0.9
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CHARMLESS HADRONIC B-DECAYS AT BABA
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surements (fL ∼ 0.5). Several att
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Estimating the Higher Order Hadroni
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the resulting exponent suggests to
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The counterpart of the ground-state
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(a) Tree level signal decay b ¯Bs
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the B0 d system LHCb profits from i
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This result is based on averaging o
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y non-perturbative effects. Using t
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e M(Dπ) distributions obtained D +
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CHARM PHYSICS RESULTS AND PROSPECTS
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LHCb is working towards its first m
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Two body hadronic D decays Yu Fushe
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where the effective coefficients aA
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6. J. J. Sakurai, Phys. Rev. 156, 1
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states: 6π, 2K4π, 4K2π, KSK3π 1
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egion of X(3872), which corresponds
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Figure 1: The π 0 recoil mass spec
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η → π + π − π 0 η ′ →
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conservation. This second principle
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many of them come from gluon nonper
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Latest Jets Results from the Tevatr
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in for the inclusive trijet event s
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RECENT RESULTS ON JETS FROM CMS F.
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dy (pb/GeV) /dp 2 d 10 10 10 9 10
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RECENT RESULTS ON JETS WITH ATLAS G
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| y| < 0.3 ATLAS Preliminary 2.1 <
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EPOS 2 and LHC Results TanguyPierog
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positions are randomly distributed
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ABOUT THE HELIX STRUCTURE OF THE LU
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Figure 2: Left: Correlations betwee
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Improving NLO-parton shower matched
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due to the inclusion of higher orde
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New Results in Soft Gluon Physics C
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Figure 2: Spacetime depiction of Dr
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Central Exclusive Meson Pair Produc
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in the CEP cross section. However i
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AN AVERAGE b-QUARK FRAGMENTATION FU
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1/N dN/dx 3.5 3 2.5 2 1.5 1 0.5 ALE
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W + W + jj at NLO in QCD: an exotic
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Σ fb Σ fb 3.5 3.0 2.5 2.0 0.65 0.
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W/Z+Jets and W/Z+HF Production at t
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Figure 2: Measured inclusive jet di
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W and Z physics with the ATLAS dete
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SHERPA 9 MC generators but not by P
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W/Z + Jets results from CMS V. CIUL
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Events / 0.1 600 500 400 300 200 10
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TEVATRON RESULTS ON MULTI-PARTON IN
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iterative midpoint cone algorithm w
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INVESTIGATIONS OF DOUBLE PARTON SCA
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¦ § ¦ ¨ ¥ ¦ ¨ § ¦ © ¦ §
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Figure 4: Two-dimensional distribut
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SOFT QCD RESULTS FROM ATLAS AND CMS
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as a function of multiplicity for t
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Determination of αS using hadronic
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α S (m Z 0) 0.15 0.14 0.13 0.12 0.
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Reaching beyond NLO in processes wi
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dσ/dp t,max [fb/GeV] 10 5 10 4 10
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Nonlocal Condensate Model for QCD S
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The lower bound for the integration
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AN ALTERNATIVE SUBTRACTION SCHEME F
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where MBorn,g is the underlying Bor
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THE NNPDF2.1 PARTON SET F. CERUTTI
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ottom masses mb of 4.25, 4.5, 5.0 a
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HOLOGRAPHIC DESCRIPTION OF HADRONS
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∫ SYM = κ d 4 ( 1 xdzTr 2 h(z)F
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Nuclear matter and chiral phase tra
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fact that for Nc ≫ 3 a gas of fre
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Recent Results on Light Hadron Spec
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Figure 3: Mass spectrum fitting wit
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MEASUREMENT OF THE J/ψ INCLUSIVE P
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2 Counts per 40 MeV/c 120 100 80 60
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STUDY OF Ke4 DECAYS IN THE NA48/2 E
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photons were accepted while particl
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6. Structure Functions Diffraction
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2 Hadronic Final States and Diffrac
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3 Summary A brief overview of recen
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Using HERA Data to Determine the In
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k f n 0.4 0.2 0 -0.2 0.4 0.2 0 -0.2
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The singular term, on the other han
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Page 334 and 335: 3 Results 3.1 Dijet Properties in p
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Page 342 and 343: Here D is the diffusion coefficient
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Page 383 and 384: 4 Low energy precision Spectroscopy
Page 385: asymmetries associated to Bd and Bs
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